Intercommunicating telephone system.



Patented May 17, 1910.

E. R. GORWIN. INTERGOMMUNIGATING TELEPHONE SYSTEM.

APPLICATION FILED sme'r za, 1907.

INVENTOR.

ANDREW a GHAKhM CO.PNOTO-LIWDGRAPMERS, wAsmNewN. a c.

WI mass ES EUTWTE @TrtTltlh T @TTTWE,

ELMER It. COEWIN, OF CHICAGG, ILLINCIS, ASSIGNOB, BY MESNE ASSIGNMENTS,TO

COR-WIN TELEPHONE MANUFACTURING COMPANY, OF CHICAGO, ILLINOIS, A COR-PORATION OF ILLINOIS.

INTERCOMMUNICATING TELEPHONE SYSTEM.

Specification of Letters Patent. Patentgd Maw 17, 19mm, Applicationfiled September 23, 1907.

Serial 1%. 394,129.

To all whom it may concern:

Be it known that I, ELMER R. CoRwIN, a citizen of the United States ofAmerica, residing at Chicago, in the county of Cook and State ofIllinois, have invented a new and useful Tntercommunicating TelephoneSystem, of which the following is a specification, referencebeing had tothe accompanying drawing, illustrating same.

My invention relates to telephone systems, and in particular to suchsystems wherein a plurality of parties at respective stations may calleach other and communisystem which is metallic throughout; to provideimproved means for ringing the several parties on the system; to improvethe impedance arrangement from the several lines to the central sourceof current; to decrease the number of conductors leading to a telephoneset in such a system; and to provide general improvements.

Other objects will be apparent from the following specification.

Generally stated my present invention provides a telephone system inwhich a number of stations are connected through impedances to a centralsource of electrical supply, each station being so arranged on thesystem that by means of suitable switching mechanism thereat it may beconnected with any 01": the other stations on the system as desired,without the intervention of the ordinary telephone central switchboard,for communication between any two parties on the system, such connectionalso permitting any of the other parties on the system to simultaneouslyconverse with each other. At each station on the system is also providedswitching mechanism whereby each of the parties on the system may ringany of the other stations as desired, to signal same for a connection.The system is also provided with switching mechanism whereby any of theparties on the system maycall outto a central exchange over suitabletrunk lines, one of the stations on the system (called the attendantsstation) being provided with signaling apparatus on the trunk lines forreceiving incoming trunk calls, and suitable switching mechanism foranswering the trunk calls.

The accompanying drawing illustrates diagrammatically a number ofstations and trunk lines on the system of my invention, with suitableconnections for the operation and utilization thereof.

The apparatus at the various stations, 1, 2, 3, etc, is included betweenlines f g, g 2', 2' is, etc., respectively.

Each of the stations on the system is provided with a plurality ofpush-button keys, such as T, T, H, 1, 2, 3, etc, each key being providedwith a pair of spring contact members 4 5 adapted to engage a pair ofcontact members 6, 7, respectively, when the pushbutton 8 is depressed,and to lock in this depressed position so as to keep the said contactsclosed. Each push-button switch or key is also provided with a contactmember 10 adapted to engage contact member 7 when the push-button 8 isdepressed past the looking position. All of the keys at any one stationon the system are connected with a common locking mechanism whereby thedepression of any one of the push-buttons releases any of the other keysat this station which may be in locking position, and allows same toreturn to normal position, each key being so constructed that it willreturn to its normal position when the locking mechanism is released.

As there are known in the art several different locking keys and banksof keys which could be readily adapted for use in connection with thisinvention, it is not thought to be necessary to herein describe, indetail, any particular locking mechanism for the keys herein shown. Inthis connection it is believed to be su'llicient to merely state thateach of the keys shown in the drawing locks in a position in which ringmembers 4 and 5 engage contacts 6 and respectively, and that each key iscapable of being further depressed until contact 7 engages contact 10,not looking in this latter position, but returning to the aforesaidlocking position when the pressure is removed from the button 8. At eachstation on the system is a push-button key H called the home key, whichconnects the transmitter 19 and receiver 20 at that station across theline of that station for use.

The local lines of the intercommunicating system are designated on thedrawing by 0, d and 6, respectively. Each of the keys at a station isadapted to connect the transmitter 19 and receiver 20 of that stationacross the various local lines of the system, respectively, or across atrunk line. At each station on the system is provided aninterrupted-current ringer 11 adapted to be rung from a central battery12 through an inter rupter 13, from any of the other stations on thesystem. The ringers 11 11 are rung from a pulsating current from battery12, produced by the interrupter 13 when the circuit of battery 12 isclosed through the interrupter 13 and a ringer 11. WVhen this lattercircuit is closed the operation of the interrupter 13 is a follows:First the current through the double coil magnet 39 of interrupter 13causes the armature 10 thereof to be attracted to the poles of themagnet, the armature thus breaking contact 41 42 and closing contact 1243 which latter contact now connects battery 12 direct with conductor21. As contact e1 12 is now broken, the magnet 39 becomes deenergizedwhereupon the armature 4:0 recedes from the poles of magnet 39, therebyopening contact 43- 42 and closing contact 12 a1. Now the magnet becomesrenergized with current from battery 12 and again produces the cycle ofoperations just described above. It will be seen that with thisinterrupter a pulsating current is produced which has double thefrequency of such a current produced by ordinary interrupters such asbuzzers or direct-current bells. WVith this high frequency pulsatingcurrent the ringers 11 11 may be rung harder, even with a sloweroperation of the interrupter 13. Each ringer 11 serves as an impedancefrom the central talking battery let to one side of its line, therebeing provided an impedance coil 15 connected from the central talkingbattery 14: to the other side of the line, for each station. There areno contacts at the ringers 11 11 to be operated when the ringer isoperated, each ringer simply comprising a double-coil magnet 36 bridgeddirect from conductor 23 to the corresponding line conductor 22, andhaving a spring 37 for pulling the armature 38 away from the poles ofthe magnet when the latter is not magnetized. Such a ringer may beoperated with a pulsating current in either direction in the circuit andis therefore not a polarized ringer. It is clear, however, thatpolarized ringers could be used at the several stations on the system ofthis invention. Across each trunk line a, Z), etc., at the attendantsstation, are bridged a ringer 16 and a condenser 17, through which theoperator at a central exchange may send a ringing current to signal theattendant on the intercommunicating system. On each of the trunk linesis also provided a relay 18, at the attendants station, which isarranged to automatically bridge itself across the trunk line when thetrunk key at the attendants station is depressed so that contact 7engages contact 10, to avoid giving a disconnect signal on the trunkline to the operator at the central exchange when the attendant pressesa localline key at his station to call a local station and therebyreleases the trunk key. This will be more fully described in thedescription of the operation of the system.

The operation of the system is as follows: To show how one party on thesystem calls another party on the system and how connection is made forconversation between these two parties, I will assume that the party atstation 1 calls the party at station 3, and will trace the operationsand connections necessary to enable the party at station 1 to conversewith the party at station 3. It will be understood that any party on theintercommunicating system may call and converse with another party onthe system in a manner similar to that next hereinbelow described, evenif other stations on the system are busy; the ringing circuits havingone individual conductor, and a common-return, for each ringer, and thetalking circuits being metallic throughout. In calling the party atstation 3, the party at station 1 first depresses his push-button key 3to the ringing position, that is until contact 7 thereof engages contact10, and thereby closes a circuit from ringing battery 12 throughinterrupter 13, conductor 21, contact 10 7 of key 3 at station 1, limb22 of line 0, ringer 11 of station 3, and conductor 23 back to battery12. Current from battery 12 now flows through interrupter 13 and ringer11 at station 3, and thereby rings the ringer 11 due to the interruptedcurrent produced by the interrupter 13 in a manner hereinbeforedescribed. It will be readily seen that the interrupted-current ringer11 at station 3 could be replaced by an alternating-current ringer ifthe interrupter 13 were replaced by a polechanger placed in a pair ofconductors leading from battery 12 and connecting with conductors 21 and23, respectively. hen party 1 has rung station 3 sufliciently, hereleases his key 3 which returns to locking position, that is, to theposition in which spring members 4: and 5 en age contacts 6 and 7,respectively, contact 10 7 being open, and then removes his receiver 20from the switch hook 25 which bridges his transmitter 19 and receiver 20through conductors 29 and 30 of station 1, and through contacts 4 6 and5 7 of key 3 at station 1, across the limb 28 and 22 of line 6.Conductors 29 and 30 extend to all of the spring members 4: and 5,respectively, of the several pushbutton keys or switches at thisstation. The party at station 3 answers his call by lifting his receiver20 from the switch hook 25 which connects with contacts 26 and 27, andthen depresses his home key H to locking position which bridges histransmitter 19 and receiver 20 across the limbs 22 and 28 of hismetallic line 6. Now the talking circuit is closed from transmitter 19at station 1, through conductor 29 at station 1, contact 1 6 of key 3 atstation 1, limb 28 of line 6, contact 6 1 of key H at station 3,transmitter 19, receiver 20 and switch hook 25, at station 3, contact 57 at key H of station 3, limb 22 of line 6, contact 7 5 of key 3 atstation 1, conductor 30, and switch hook 25 and receiver 20, at station1, back to transmitter 19 at station 1. This talking circuit is fed withcurrent from talking battery 14 through impedance coil 15 and the coils36 of ringer 11 corresponding to station 3, which are connected frombattery 14 to limbs 28 and 22, respectively, of line 6.

The impedance coil 31 at each of the stations is of high impedance andof low resistance compared to the resistance of re ceiver 20, and isprovided as a shunt around receiver 20 so as to take most of thedirectcurrent supply flowing throughthe transmitter 19 and at the sametime allow receiver 20 to take approximately all of the talking currentspassing through the transmitter 19. The direct current which sup pliesthe transmitter 19 is thus shunted from the receiver 20 so that thelatter will not become demagnetized or over magnetized thereby.

When the conversation between parties 1 and 3 is completed these partieshang up their receivers on their respective switch hooks, which opensthe circuits of their talking sets at the respective switch hooks andthereby stops the flow of current from bat tery 14 over the aforetracedtalking circuit between stations 1 and 3. Party 1 leaves his key 3'depressed until he desires to use his line again, either incommunication with station 3 or any of the other stations or trunk linesof the system. The depression of any of the other keys at station 1,when it is desired to again use the talking set at station 1, releasesthe key 3 as hereinbeforc stated.

Party 3 also leaves his home key H depressed until he desires to use histalking set again, his key H being restored by the depression of any ofhis other keys, as just stated in connection with station 1.

It any of the parties of the mtercommunieating system deslres to make anoutgolng trunk call over a trunk line, as for example the party atstation 2 calling out over trunk line a, he depresses his trunk key Tcorresponding to the trunk line, to locking position, and then removeshis receiver 20 from the switch hook 25 which bridges his transmitter 19and receiver 20 through conductors 29 and 30 at his station, andcontacts 4t 6 and 5 7, respectively, of his trunk key T, across thelimbs 32 33 of the toll line a, which signals the central-energyexchange to which the trunk line a leads, the same as any ordinarycentral-energy subscriber signals his central oilice. Conversation maybe now carried on over the trunk line a the same as in an ordinarycentral-energy telephone system. lVhen the conversation is completed theparty at station 2 hangs up his receiver 20 on the switch hook 25 andthereby breaks the circuit between the limbs 32 33 of the toll line a,at the switch hook 25, and thus gives the usual disconnect signal to theoperator at the central exchange. The party at station 2 leaves histrunk key T depressed until he desires to use his talking set again, hiskey T being restored by the depression of any of his other keys, asstated above in connection with stations 1 and 3.

The attendant, shown in the drawing at station 1, answers all of theincoming trunk calls to the intercommunicating system as follows: Whenthe operator at the central exchange desires a connection with a stationof the intercommunicating system, she rings the ringer 16 of the trunkline a (or 7)) in the usual manner, whereupon the attendant depresseshis trunk key T corresponding to the trunk line, to locking position andthen removes his receiver 20 from the switch hook 25 which bridges histransmitter l9 and receiver 20 through conductors 29 and 30 of station1, and contacts 4c 6 and 5 7, respectively, of key T at station 1,across the limbs 32 33 of the trunk line (4. Now the attendant converseswith the party connected from the central exchange over the trunk lineand learns from him the station of the intercommunieating system withwhich communication is desired. Assuming this latter station to bestation 2 of the intercommunicating system, the attendant proceeds tocall station 2 by first depressing his trunk key T to ringing positionand simultaneously hanging his receiver 20 upon the switch hook 25 whichdisconnects him from the toll line, andthen depressing his key 2 toringing position which signals the party at station 2 by closing thecircuit of battery 12 through interrupter 13, conductor 21, contact 10 7of key 2 at station 1, limb 22 of line (i, ringer 11 of station 2, andconductor 23 back to battery 12. The attendant by depressing his trunkkey T to ringing position as he hangs up his receiver 20, bridges thetrunk relay 18, corresponding to trunk line a, through contact 10 7 ofkey T of station &

1, across limbs 32 33 of the trunk line a, whereupon the relay 18attracts its armature 3 1 and thereby closes contact 34: 35 whichpermanently bridges the winding of relay 18 across the limbs 32 33 ofthe trunk line after the key T returns to lockin position in whichposition the contact 10 3 is open. Bridging the relay 18 across thetrunk line in this manner is for the purpose of holding the line, or toavoid giving a disconnect signal when the attendant hangs up hisreceiver 20 which opens his talking set bridge across the limbs of thetoll line, until the party 2 answers the trunk call as directed by theattendant.

When the attendant depresses his key 2 to signal the party at station 2,he automatically releases his key T and restores same to normal positionin which position all of the contacts of the key are open. When theparty 2 answers the signal of his ringer 11, he depresses his home key Hto locking position and removes his receiver 20' from the switch hook 25which bridges his transmitter 19 and receiver 20 across the limbs 28 22of his line d, as hereinbefore described. The attendant upon removinghis receiver 20 from the switch hook 25, after his key 2 returns tolocking position, bridges his transmitter 19 and receiver 20 throughconductors 29 and 30 of station 1, and contacts 4 6 and 5 7,respectively, of his key 2, across the limbs 28 22 of line 0? so that hecan converse with the party at station 2 and instruct him to come in onthe trunk linea to answer the trunk call. Now the party at station 2depresses his trunk key T, which releases his home key H, and therebybridges his transmitter 19 and receiver 20 through conductors 29 and 30of station 2, and contacts 4 6 and 5 7, respectively, of trunk key T atstation 2, across the limbs 32 and 33 of the trunk line a. Now the partyat station 2 may converse with the party who is connected from thecentral exchange through the trunk line a, transmitter 19 of station 2being supplied with talking battery from the central exchange over thetrunk line a. The talking set of station 2 being of low resistancecompared with the resistance .of relay 18 of trunk line a, now shuntsthis relay and causes same to release its armature and thereby break thecontact 3& 35 which breaks the bridge of this relay 18 across the trunkline a. Now when conversation is completed and the party at station 2hangs up his receiver 20 on the switch hook 25, he breaks the bridge ofhis talking set across the trunk line a at his switch hook and therebyopens the circuit of the trunk line and thus gives the usual disconnectsignal to the operator at the central-energy exchange. The party atstation 2 leaves his trunk key T depressed to locking position until hedesires to use his talking set again, when the depression of any one ofthe other keys at his station releases the trunk key T.

It will be readily seen that the ringing and talking keys of this systemare self-indicating, that is, they indicate the party with whomconversation was last had, or, in the case of calling a party who doesnot respond, they indicate the station with which communication isdesired, so that the calling party may again readily depress the properkey to ringing position to signal the called party a second time. Itwill also be seen that in this system only two conductors are requiredat each of the stations to connect the talking sets thereof with thesystem. This greatly simplifies the wiring which is necessary to connecta talking set with. the system, over other systems where more than twoconductors are required to connect a talking set with the system.

I do not wish to limit this invention to all of the particular detailsherein shown, as many modifications of same may be made withoutdeparting from the scope of the appended claims.

What I claim as my invention is:

1. The combination with an intercommunicating telephone system having aplurality of stations and a trunk line common thereto, of a relay, a keyadapted in itself to bridge the relay across the trunk line,independently of the condition of the other apparatus of the system, anda switch controlled by the relay whereby the latter when bridged acrossthe trunk line by the said key maintains its own bridge after the keyhas been released, until properly deenergized, for purposessubstantially as described.

2. The combination with an intercommunicating telephone system having aplurality of stations and a trunk line common thereto, of a relay, meansfor bridging the relay across the trunk line to hold the latter whilecalling the called station, the said relay being adapted to control itsown bridge, and means whereby the telephone set of the said calledstation, when connected with the trunk line for use, forms a directshunt around the said relay to deenergize the latter sufficiently tocause it to break its own bridge, for purposes substantially asdescribed.

3. The combination with an intercommunicating telephone system having aplurality of stations and a trunk line common thereto, of a relay, a keyadapted in itself to bridge the relay across the trunk line,independently of the condition of the other apparatus of the system, tohold the trunk line while calling the called station, a switchcontrolled by the relay whereby the latter when bridged across the trunkline by the said key maintains its own bridge after the key has beenreleased, and means whereby the telephone set of the said calledstation, subscribe my name in the presence of two When connected withthe trunk line for use, subscribing Witnesses, this 19th day of Sepformsa direct shunt around the said relay tember, 1907.

to denergize the latter sufliciently to cause ELMER R. CORWIN. 5 it tobreak its own bridge, for purposes sub- Witnesses:

stantially as described. FREDERICK R. PARKER,

As inventor of the foregoing I hereunto H. ROY 000K.

